wheels and rubber

[Dong xia]

My friend asked me why F1 cars' wheels have such thick tyres? He found the super sports cars have hugh rim with thin tyre,but the fastest cars on the circuit have very thick rubber. He don't understand why and asked me, who seem to know something about F1. However, , I don't know the standard answer, either. Please, help!

[arisen]

I was wondering myself about that... With a higher sidewall tire the loss of grip is more gradual, giving an advanced warning before the car starts to skid. The tire deforms and stretches a bit more off the rim before it looses grip sideways, giving the driver more feel on the limit of adhesion. With a low profile tire the car is more responsive and has more directional stability. So there are advantages both ways, and most probably the size is dictated by regulation anyway.

On my road car for ex I tried both 14 inch and 17 inch rims and tires, and I prefer the 14” hands down. Being a FWD it’s massively understeering, and with the 14” I get a much better feel as to how much steering input I can use, before it starts plowing off the road.

[Steven]

Well now that you mention, here are the regulations that are appropriate for the wheelsize and tire-thickness

12.4.2 Complete wheel diameter must not exceed 660mm
when fitted with dry-weather tyres or 670mm when fitted
with wet-weather tyres.
12.4.4 Wheel bead diameter must lie between 328 and 332mm.

[Garretto]

I always wondered about why F1 wheels were so small compared to tire wall. The actual reason seems to be regulations but then the question that arises is this one:

What diameter would F1 wheels have (and what % sidewall) if it wasn't regulated by FIA??? That is, which would be the most effective relation between wheel diameter and sidewall heighth?

Please consider all areas involving this matter: aerodynamics, weight, performance, brake cooling, grip, steering precision...

I look forward to hearing your comments

[dumrick]

As far as I know, the trend of mounting radically big rims in low profile tyres in high performance and sports cars is mainly due to the possibility of having larger diameter brake discs.
As arisen said is a matter of trade-off between turn responsiveness/straight line stability and feedback/comfort/grip.
As far as sheer grip is concerned, I'm fairly sure that higher tyres have the advantage, being able to adjust the contact patch in a higher extent when submitted both to longitudinal and lateral forces.

[Irvingthien]

From my point of view, the thinner the tyre, the faster the heat biulds up. If you drive an F1 car with thin tyres and large rims, just like in supercars racing, it will be like driving a wet weather tyre on dry conditions.
F1 cars are like 5 times faster than supercars and the friction produced is much higher, which generates more heat.

[Garretto]

I think that if wheel/tire/brake diameters were not regulated by FIA the sizes would be pretty much similar to those of Sports-GT racecars, which look like a good compromise between braking performance, sidewall bending, tire heating, etc.

That is, the aspect ratio would change to a lower profile tire with bigger wheel.

Just my 0.02 €